Alternating current conductivity and spectroscopic studies on sol-gel derived, trivalent ion containing silicate-tetra(ethylene glycol)-based composites

Abstract

Sol-gel derived, composite solid ionic conductors containing the triflate salt of europium(III) in silicate-tetraethylene glycol matrices have been prepared. The ionic interactions in the matrix are followed using vibrational spectroscopy. The quantitative estimations of various species such as free ions, ion pairs, and aggregates in the organically modified electrolyte (ormolytes) suggest that the free ion concentration is considerably high. This is in contrast to the formation of large fractions of ion pair expected for high-valent cations with triflate. The ionic conductivity is found reach values of 10^-3 S/cm at 80°C. The temperature dependence of ionic conductivity is observed to follow pure Arrhenius-type behavior. The high-frequency ac impedance behavior of the ormolyte has been explained on the basis of the universal power law equation related to the "jump relaxation model" framework. The conductivity relaxation time, ^τpeak, has been evaluated from the complex resistivity relaxation spectra. It is suggested that anion conduction predominates over cations at low temperatures while the trend is toward cation conduction at high temperatures.